109 lines
3.5 KiB
C++
109 lines
3.5 KiB
C++
/*
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StackThunk - Implements a simple 2nd stack for BSSL and others
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Copyright (c) 2022 Earle F. Philhower, III. All rights reserved.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <stdint.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include "StackThunk.h"
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extern "C" {
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uint32_t *stack_thunk_ptr = nullptr;
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uint32_t *stack_thunk_top = nullptr;
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uint32_t *stack_thunk_save = nullptr; /* Saved A1 while in BearSSL */
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uint32_t stack_thunk_refcnt = 0;
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/* Largest stack usage seen in the wild at 6120 */
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#define _stackSize (6400/4)
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#define _stackPaint 0xdeadbeef
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/* Add a reference, and allocate the stack if necessary */
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void stack_thunk_add_ref() {
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stack_thunk_refcnt++;
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if (stack_thunk_refcnt == 1) {
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// The stack must be in DRAM, or an Soft WDT will follow. Not sure why,
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// maybe too much time is consumed with the non32-bit exception handler.
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// Also, interrupt handling on an IRAM stack would be very slow.
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// Strings on the stack would be very slow to access as well.
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stack_thunk_ptr = (uint32_t *)malloc(_stackSize * sizeof(uint32_t));
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if (!stack_thunk_ptr) {
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// This is a fatal error, stop the sketch
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abort();
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}
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stack_thunk_top = stack_thunk_ptr + _stackSize - 1;
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stack_thunk_save = nullptr;
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stack_thunk_repaint();
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}
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}
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/* Drop a reference, and free stack if no more in use */
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void stack_thunk_del_ref() {
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if (stack_thunk_refcnt == 0) {
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/* Error! */
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return;
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}
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stack_thunk_refcnt--;
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if (!stack_thunk_refcnt) {
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free(stack_thunk_ptr);
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stack_thunk_ptr = nullptr;
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stack_thunk_top = nullptr;
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stack_thunk_save = nullptr;
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}
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}
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void stack_thunk_repaint() {
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for (int i = 0; i < _stackSize; i++) {
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stack_thunk_ptr[i] = _stackPaint;
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}
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}
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/* Simple accessor functions used by postmortem */
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uint32_t stack_thunk_get_refcnt() {
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return stack_thunk_refcnt;
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}
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uint32_t stack_thunk_get_stack_top() {
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return (uint32_t)stack_thunk_top;
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}
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uint32_t stack_thunk_get_stack_bot() {
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return (uint32_t)stack_thunk_ptr;
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}
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uint32_t stack_thunk_get_cont_sp() {
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return (uint32_t)stack_thunk_save;
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}
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/* Return the number of bytes ever used since the stack was created */
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uint32_t stack_thunk_get_max_usage() {
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uint32_t cnt = 0;
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/* No stack == no usage by definition! */
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if (!stack_thunk_ptr) {
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return 0;
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}
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for (cnt = 0; (cnt < _stackSize) && (stack_thunk_ptr[cnt] == _stackPaint); cnt++) {
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/* Noop, all work done in for() */
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}
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return 4 * (_stackSize - cnt);
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}
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};
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